1
Introduction
A transportation indicator is a measure of change over time in the transportation system or in its social, economic, environmental, or other effects. Two National Research Council (NRC) studies recommended, as a matter of high priority, that the Bureau of Transportation Statistics (BTS) in the U.S. Department of Transportation (USDOT) develop a consistent, easily understood, and useful set of key indicators of the transportation system. The NRC’s Committee on National Statistics and its Transportation Research Board, which conducted these studies, convened a workshop on June 13, 2000.1 The purpose of the Workshop on Transportation Indicators was to discuss issues relating to transportation indicators and provide the Bureau of Transportation Statistics with new ideas for issues to address. Most statistical agencies produce monthly, quarterly, or annual indicators in their areas. Examples are monthly reports of the Consumer Price Index (CPI) and the unemployment rate by the Bu-
reau of Labor Statistics; quarterly reports of gross domestic product (GDP) by the Bureau of Economic Analysis; and annual reports of poverty, high school completion and dropout rates, and births, deaths, and other vital statistics by the U.S. Census Bureau, the National Center for Education Statistics, and the National Center for Health Statistics, respectively. These indicators are important for public policy decision making. Some of them have significant effects on the economy and private-sector decisions. And, in an important sense, all of them serve to hold the government accountable to the public.
BTS is the newest federal statistical agency, established by the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA) and subsequently reauthorized. The authorizing legislation charges BTS to work with other USDOT administrations, the states, and other federal officials to implement a long-term program for collecting and analyzing data on the performance of the national transportation system.
From its inception, BTS has compiled myriad indicators based on data that are regularly collected on the transportation system. These data serve many important purposes. They help to increase understanding of interactions between transportation activity and the economy, the environment, and community development and other land use. They are used to monitor changes in the performance of the transportation system, which may alert us to possible future problems. And they are useful directly in managing the transportation system. For these purposes, the data are mostly used within administrations of USDOT with responsibility over particular transportation modes, such as the Federal Highway Administration and the Federal Transit Administration and within state and local agencies, such as metropolitan planning organizations (MPOs).
But, among these many indicators, how can we select those that are most significant to public policy and to public awareness? Which of them are important measures of accountability? What indicators are most relevant to major transportation policy concerns? What indicators are most appropriate for BTS to develop in its role as a statistical agency that is concerned with broad transportation issues and all transportation modes?
This workshop considered questions such as these. Participants were also asked to think creatively about aspects of the performance of the transportation system that should be measured with indicators but are not. Are there useful, feasible indicators that are important to develop that cut across modes? Should safety indicators be based on the risk of a type of journey,
or should they incorporate the transportation patterns of individuals? For some indicators, such as congestion, is it more meaningful to report them for a few major cities or metropolitan areas than to report them on a national level? Data from the 2000 census provide opportunities for developing new local indicators because of new definitions for metropolitan areas and the fact that transportation analysis zones will follow the boundaries of census geography. For new indicators, are the needed data available? If not, what conceptual and measurement problems need to be addressed?
USDOT has developed five strategic goals that are useful in identifying key policy areas for which indicators could be helpful. The five goals are in the areas of (1) safety, (2) mobility, (3) economic growth and trade, (4) human and natural environments, and (5) national security. The workshop focused on the first three areas for case studies. Separate groups of participants considered these areas in advance of the workshop and presented suggestions for key indicators with a discussion of conceptual, measurement, and data issues at the workshop. Indicators for the transportation of people, in contrast to freight, received most attention, although freight indicators were part of the scope for the third case study.
Each of the subgroups was to review the current indicators, review the available data to support them, and identify the issues associated with their use. The separate groups conferred in person, by telephone, or by email to consider indicators and address issues in their respective areas: (1) safety, including measures within and across modes; (2) mobility, including congestion, access to transportation in rural areas, and the condition of infrastructure and its maintenance required to meet future demand; and (3) economic growth, including the movement of freight.
The members of the safety subgroup were:
Kenneth L. Campbell (Chair), Transportation Research Institute, University of Michigan
Lindsay Griffin, Texas Transportation Institute
Charles A. Lave, Department of Economics, University of California, Irvine
John S. Miller, Virginia Transportation Research Council
Douglas Robertson, Highway Safety Research Center, University of North Carolina
Nathaniel Schenker, National Center for Health Statistics
BTS Liaison: Terry Klein, Bureau of Transportation Statistics
The members of the mobility subgroup were:
Michael Meyer (Chair), School of Civil and Environmental Engineering, Georgia Institute of Technology
David L. Greene, Oak Ridge National Laboratory
Randall K. Halvorson, Minnesota Department of Transportation
Timothy J. Lomax, Texas Transportation Institute
Alan E. Pisarski, consultant, Falls Church, VA
Anthony E. Smith, Department of Systems Engineering, University of Pennsylvania
Clifford H. Spiegelman, Department of Statistics, Texas A&M University
Ronald W. (Ron) Tweedie, New York State Department of Transportation
BTS Liaison: Alan F. Karr, National Institute of Statistical Sciences
The members of the economic subgroup were:
Damian Kulash (Chair), Eno Transportation Foundation, Inc.
Randall Eberts, Upjohn Institute
Francis Francois, American Association of State Highway and Transportation Officials (former executive director)
Barbara M. Fraumeni, Bureau of Economic Analysis
Richard (Dick) Mudge, Compass Services
M. Ishaq Nadiri, Department of Economics, New York University
BTS Liaison: Rolf Schmitt, Bureau of Transportation Statistics
Each group developed a preliminary set of a few key indicators, cutting across modes when appropriate and considering the appropriate level of geographic detail (national, state, or local). For example, for transportation safety, indicators included numbers of fatalities and injuries as well as fatality and injury rates by mode. For mobility, indicators included hours of delay and time and distance of commute trips. For economic growth, indicators included percentage on-time performance, average daily value of inventory in transit, value of goods damaged in transit, and cost per trip and unit of travel.
The groups prepared written statements summarizing their results for presentation and distribution at the workshop. The chair of each group presented the results and led a discussion. The groups raised issues that they identified while developing their indicators, including measurement issues (e.g., appropriate measures of exposure), data availability and timeli-
ness, consistency across modes, and appropriate reporting frequency and gave suggestions about how these issues might be addressed.
In addition to the three subgroups, Diane Herz from the Bureau of Labor Statistics also gave a presentation at the workshop. She discussed the American Time-Use Survey as it specifically relates to transportation statistics. She presented potential transportation statistics that could be gleaned from the survey, such as the purpose of trips and the time spent traveling. Appendix A is a summary of her presentation.
